The invention relates to water soluble and dispersible oligomers, and efficient methods to prepare these new oligomers.
Water soluble and dispersible polymers are in great demand for use as surfactants. Low molecular weight amphiphilic compounds can also be used as surfactants. For example, fatty acid esters of carbohydrates are useful as surfactants. The incorporation of carbohydrates into water soluble and dispersible polymers is thus a promising strategy for the design of new amphiphilic compounds.
There are some potential difficulties in the conversion of carbohydrate building blocks into oligomers and polymers. Carbohydrates contain multiple hydroxyl groups; some of these groups have similar reactivities, making regioselective reactions difficult to achieve. Chemical methods involving multiple protection/deprotection steps for the regioselective esterification of carbohydrates and their derivatives have been studied. The protection/deprotection steps can be eliminated with the use of biological catalysts, such as enzymes. Specific enzymes which include lipases and proteases have been successfully used for the regioselective esterification of the primary hydroxyl groups of various carbohydrates in polar aprotic solvents.
For example, Therisod et al., J. Am. Chem. Soc. 108:5638 (1986), reported the regioselective esterification of various carbohydrates, using porcine pancreatic lipase (PPL) as the enzyme and pyridine as the solvent. Riva et al., J. Am. Chem. Soc. 110:584 (1988), disclosed the PPL-catalyzed regioselective esterification of carbohydrates in dimethyl formamide (DMF). In addition, Adelhorst et al., Synthesis 112 (1990), described regioselective esterifications in the absence of solvent; they reported the solvent-free esterification of ethylglucoside with fatty acids using Candida antarctica lipase as the catalyst.